AUDITORY EVENT-RELATED POTENTIALS RECORDED DURING PASSIVE LISTENING AND SPEECH PRODUCTION

Abstract: What is the role of audition in the process of speech production and speech perception? Specifically, how are speech production and speech perception integrated to facilitate forward flowing speech and communication? Theoretically, these processes are linked via feedforward and feedback control subsystems that simultaneously monitor on-going speech and auditory feedback. These control subsystems allow self-produced errors to be detected and internally and externally generated speech signals distinguished. Auditory event-related potentials were utilized to examine the link between speech production and perception in two experiments. In Experiment 1, auditory event-related potentials during passive listening conditions were evoked with nonspeech (i.e., tonal) and natural and synthetic speech stimuli in young normal-hearing adult male and female participants. Latency and amplitude measures of the P1-N1-P2 components of the auditory long latency response were examined. In Experiment 2, auditory evoked N1-P2 components were examined in the same participants during self-produced speech under four feedback conditions: nonaltered, frequency altered feedback, short delay auditory feedback (i.e., 50 ms), and long delay auditory feedback (i.e., 200 ms). Gender differences for responses recorded during Experiments 1 and 2 were also examined. Significant differences were found for P1-N1-P2 latencies and for P1-N1 and N1-P2 amplitudes between the nonspeech stimulus compared to speech tokens and for natural speech compared to synthetic speech tokens in Experiment 1. These findings were attributed to differences in the spectro-temporal characteristics of the tokens. In Experiment 2, there were no significant differences in N1-P2 latencies and amplitudes across feedback conditions. To examine differences between component latency and amplitude during passive listening and active speaking, responses elicited via passively presented self-produced nonaltered and frequency altered tokens were compared to the nonaltered and frequency altered feedback active conditions. Significantly, smaller N1-P2 component amplitudes were recorded during the active versus passive speaking conditions. This finding is in accordance with research supporting feedforward and feedback theories. To further understanding of cortical processing during speech production and speech perception additional investigations are warranted in both those with normal speech and language and those with pathological speech and language, specifically, those with a speech motor disorder such as developmental stuttering.